Initialization and initial imbalance problem were discussed in the context of a three-dimensional variational data assimilation system of the new generation"Weather Research and Forecasting Model". Several options of digital filter initialization have been tested with a rain storm case. It is shown that digital filter initialization, especially diabatic digital filter initialization and twice digital filter initialization, have effectively removed spurious high frequency noise from initial data for numerical weather prediction and produced balanced initial conditions. For six consecutive intermittent data assimilation cycles covering a 3-day period, mean initialization increments and impact on forecast variables are studied. DFI has been demonstrated to provide better adjustment of the hydrometeors and vertical velocity, reduced spin-up time, and improved forecast variables quantity.
为了对台风流场的复杂结构进行研究,采用二次变分方法对台风风场进行分解.首先,将台风的流场分解成最大的、不对称的涡旋流场和无旋流场;然后将不对称的涡旋流场分解成最大的对称涡旋和不对称的β涡旋对;最后,利用WRF(weather research and forcasting)模式(V2.1.2)模拟了200601号珍珠台风,并对各时次的500hPa风场用该方法进行分解,结果表明:该方法对台风的运动机理研究和实际的台风路径预测提供了有价值的信息.
为了分析天气研究及预报WRF(weather research and forecasting)模式对我国天气现象的适用性,利用WRF模式对2003年淮河汛期的3次梅雨锋暴雨过程进行了一组数值模拟试验,对3次天气过程模拟试验采用相同的参数设置,模拟区域根据实况降水落区作了相应设置。模拟结果分析表明,WRF模式能有效模拟我国梅雨锋暴雨的环流背景和天气形势,较好地反映影响暴雨的中尺度系统的发生和发展等特征,还可以较好地模拟出雨带的范围、位置和走向,对降水中心的模拟基本可用。
